Tackifiers and softeners for synthetic rubbers and compositions containing the same



Patented Sept. 23, 1952 TACKIF IERS AND SOFTENERS FOR SYN- THETIC RUBBERS AND COIWPOSITIONS CONTAINING THE SAME Robert H. Barth, Ridgewood, N. J., assignor to Heyden Chemical Corporation, New York, N. Y., a corporation of Delaware No Drawing. Original-application November 13, 1944, Serial No. 563,310, new Patent No. 2,516,104, dated July 25, 1950. Divided and this application July 21, 1950, Serial No. 1 7 5,291

18 .Claims. (Cl. 260-27) My invention relates particularly tonew and novel chemical compounds and to compositions comprising said new compounds and synthetic rubbers, such as copolymers of diolefins and styrene and copolymers of diolefins and acrylonitrile. In one of its more specific aspects it relates to acetals of partial esters of certain polyhydric alcohols, such as the diabieticacid ester of pentaerythritol butyral, which are especially advantageous tackifiers and tack-imparting or tackifying softeners oi synthetic rubbers.- This application is a division of the application upon Resin-Acid Ester-Acetals of Polyhydric Alcohols, Ser. No. 563,310, filed November 13, 1944, which is a continuation in part of the prior copending application Ser. No. 525,592, filed March 8, 19M, which issued as Patent No. 2,446,257.

Synthetic rubbers, such as copolymers of butadiene and styrene (Buna-S or GR-S) and copolymers of butadiene and acrylonitrile (Buna- N, Hycar-OR, or GR-A) and the like, diiler from natural rubber in many respects, especially in the quantities and types of compounding ingredients which must be incorporated therewith and in the compound procedures which must be used to produce automobile tires and other useful articles therefrom. Carbon black, for example, must be incorporated in greater quantities in synthetic rubber of the GR-S type than in natural rubber to produce automobile tires, and special grades of carbon black must be used for the purpose. Different vulcanizing agents, softening agent and the like are also used. Softeners are generally used with both natural and synthetic rubber but, when used with these synthetic rubbers, greater proportions are required and the effects produced may be generally different from those produced in natural rubber.

When natural rubber is milled with'compounding ingredients in the conventional manner the material coheres and possesses considerable inherent tackiness. On the other hand, these syne thetic rubbers do not readily cohere and'do not have as much inherent tackiness as natural rubber. Softeners added to synthetic rubbers may improve the plasticity of themasswithout aflecting the tackiness substantially; for the most part they must be used in such quantities as to destroy at least partially what little inherent tackiness is possessed by the synthetic rubber. As a consequence, the industry has long sought softeners that improve the tackiness or coherence of synthetic rubbers and permit it to be milled and treated in much the same manner as natural rubber or substances which, when added to conventional synthetic rubber compositions, improve the tackiness of the resulting compositions, especially during milling.

It is a principal object of the present invention to provide a tackifier for synthetic rubber compositions, such as those produced from copolymers of butadiene and styrene and copolymers.

of butadiene and acrylonitrile. 1

It is a further object to provide a tackifier for such synthetic rubber compositions that will retain a considerable portion of its efiectiveness after vulcanization of the compositions. I

A further object of the invention is to provide a materia1 which may be used as both a softening and a tackifying ingredient for compositions comprising such synthetic rubbers.

, Other objects and advantages of the invention, some of which are referred to more specifically hereinafter, will be apparent torthose skilled in theart to which the invention pertains.

I have discovered that the foregoing objects are realized to a remarkable degree by the use of certain new and novel compounds which I described in the copending application Ser. No. 525,392, filed March 8, 1944, which issued as Patent No. 2,446,257. These compounds are exemplified by pentaerythritol diabietate butyral, which may possibly be representable structurally as:

and which is the reaction product of 2 mole of abietic acid (rosin), 1 mol of pentaerythri tol and 1 mol of butyraldehyde. Other compounds of this type which possess these desirable properties may be prepared from other acids of the type of abietic acid, other polyhydric alcohols, other aldehydes, and in other molecular proportions, as specified hereinafter.

The compounds or products to which the present invention is specifically directed may be prepared generally by partial esterification of glycerol, pentaerythritol, a polypentaerythritol, or mixtures thereof, which abietic acid or a similar acid or a material, such as .tall oil, containing a substantial proportion of such acids. This esterification may be effected by heating the two materials in the presence of a catalyst but it nor.- mally proceeds sufficiently rapidly without a catalyst in the temperature range from approximately Abietyb-O-Eh C to approximately 300 C. or somewhat higher. Catalysts which may be used, if desired. are sulfuric acid, p-toluenesulfonic acid, resinates and naphthenates of lithium, calcium, strontium, barium, zinc and cadmium and other soluble salts of these metals',.a's described in Burrell Patent No. 2,360,394, and the like. When pentaerythritol esters are being prepared, care should be exercised not to overheat the pentaerythritol before the esterification has proceeded to a substantial extent, since overheating may result-in the decomposition of the pentaerythritol with the formation of dark-colored products and undesirable byproducts. After the partial ester has been formed it is then reacted with an aldehyde to produce an acetal.

The reaction of the partial ester with the aldehyde may be conducted by'heating the two materials together in the presence of an acid catalyst, such as oxalic acid, hydrochloric acid, sulfuric acid or the like. It is desirable to add an inert solvent such as toluene or a saturated aliphatic hydrocarbon or petroleum fraction to prevent foaming and to aid in removing the water formed in the reaction. As the acetalization-pro ceeds, the reaction temperature may be raised. It is generallydesirable to conduct the aeetalization in an apparatus provided with a reflux condenser, separator ortrap, and a return line, and to efifect the heating in the presence of toluene or other solvent which is immiscible with water'but which forms an azeotrope with water. By using such an apparatus and such a solvent, the reactants can be heated under gentle reflux and the temperature can be more readily controlled.- In operating in this manner, the'condensed reflux liquid is collected in the separator or trap, the water is separated therefrom periodically, and the toluene is returned to the reaction mass. At

the end of the acetalization the solvent can be removed by volatilizati-on, preferably at reduced pressure, that is, by vacuum distillation;

Instead of preparing the partial ester by heating the acid and p-olyhydric alcohol together in the desired stoichiometric; proportions a complete ester may be used as the starting material. The

complete ester may be alcoholized-with glycerol,

pentaerythrltol or a polypentaerythri-tol, in the presence of catalysts, if desired, to form the partial ester. Thus pe'ntaerythritol tetra-abietate may be reacted with pentaerythritol to produce pentaerythritol diabietate in the presence of catalysts such as are disclosed in Burrell Patent No. 2,360,394.

Although, in the preparation of compounds for use as tackifiers from pentaery'thri'tol, in accordance with the process of the present invention, it is generally desirable to have two of the hydroxyl radicals of pentaeryth-ritol esterified by abietic acid or its equivalent and the remaining two acetalized by the aldehyde, these. proportions maybe varied considerably. With pentaerythritol, satisfactory products may be obtained from the reaction of one molecular equivalent to three -molecular equivalents of abietic acid and the may be acetalized.

The composition of the products which are formed has not definitely established but obviously they are somewhat more complex than indicated by the probable structure of :pentaeryth- :ritol 'diabietate butyral as given hereinabove.

The products may be pure compounds or mixtures of pure compounds, in which there may be cross-linkages between the original polyhydric alcohol nuclei through'the acetal group. A possible compound, for example, which has such cross-linkages and also has the same empirical composition as pentaerythritol diabietate butyr-al, isi' C3137 H20 0 CHzOAbietyI O-( 3H-CaH1 which is a dipentaerythritol tetra-abietate dibutyral.

The order of the esterification and acetalization may be reversed but esterification prior to acetalization is recommended and preferred because of its simplicity.

Instead of using pure abietic or sylvic acid in the production of the tackifiers or tackifyin-g softeners of the present invention, rosin ofvariamounts oi Steelesabietic acid and d-pimaric acid, may also be used to replace abietic acid, either partially or completely. Other acids of the type of abietic acid which may beused-for partial or complete replacement cfiabietic acid, are-lv-opimaric acid, d-pimaricacid and Palkin acids.

Glycerol, .pentaerythritol, polypentaerythrit ols and mixtures thereof are the preferred polyhydricalcoholsfor use in producing the compounds of the invention. Dipentaerythritol and tripentaerythritol are two of the polypentaerythritols which have been definitely isolated and identified. Pleopentaerythritol, one of the products that can be isolated from the condensationof formaldehyde and acetaldehyde in the presence of an alkali, and which has a melting point of 230" to 240 C, and a hydroxyl con-tentof 33%, possesses some of the attributes oia pure compound, but is a mixture of dipentaerythritol and tripentaerythritol with other hydroxylated prod-- ucts. 'Tetrapentaerythritol and higher polypentaery-thritols have been postulated at the present time. I

The ipolyhydric alcohols which may be-used for-the production of tackifying compounds in accordance with the invention are relatively restricted. Thus, ethylene glycol, propylene glycol, diethylene glycol and-the-like do not produce compounds which exhibit to any-substantial-extent the desirable properties possessed by acetals of abieticesters of glycerol, pentaerythritol and polypentaerythritols- The effect of using a diethylene glycol diabietate butyral in a butadienestyrene copolymer is illustrated in the preparation entitled Comparison'composition 1 hereinafter.

The aldehydes which may be used in the production of the acetals ofabietic acid esters of polyhydric alcohols in accordance with the process of the invention are formaldehyde, acetaldehyde, propionaldehyde, 'butyraldehyde and other aliphatic aldehydes having up to and including eight carbon atoms in the molecule. Aromatic aldehydes such as benzaldehyde may also:be used. Instead of using an aldehyde itself, the starting material may be a partially acetalized polyhydric alcohol, for example, a mixture of formals of pentaerythritol and polypentaerythritols such as is formed as a byproduct in theproduction of pentaerythritol and polypentaerythritols by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst. V x

The preferred products of the invention are those in which all the hydroxyl groups of the polyhydric alcohol have been combined, that is, some with abietic acid or its equivalents and some with an aldehyde. However, compounds with a free hydroxyl group or mixtures containing some compounds having uncombined hydroxyl groups. as well as compounds of this type in which one or moreof the hydroxyl groupszhas been esterified by acetic acid or other aliphatic or aromatic acids, may be used also.

Although the acetals of abietic esters of polyhydric alcohols which are described herein are especially adapted for use with synthetic rubbers of the types represented by copolymers'of butadiene and styrene (GR-S) and copolymers of butadiene and acrylonitrile (GR-A) they may be used generally withall synthetic rubbers which are copolymers of a 1,3-butadiene hydrocarbon and another unsaturated compound which contains a CHFC= group and is copolymerizable therewith.

In the following examples, which construed as limitative of the invention, are described methods of preparing suitable compounds for use as tackifying agents in accordance with the process of the invention. Following these examples are illustrated typical compositions containing synthetic rubber and these tackifying agents and results of vulcanizzlng or curin tests of such compositions.

Example 1.-Pentaerythritol diabietate butyral A mixture of 2000 parts of rosin (acid number=162) and 417 parts of technical pentaerythritol (hydroxyl value=46.5%; combining weight=36) was heated for two hours at 280 C. under an atmosphere of carbon dioxide. 'Ihe mixture was then cooled to approximately 80 C. and 236 parts of butyraldehyde were slowly added. During the slow addition of the butyraldehyde, concentrated hydrochloric acid was added dropwise until 55 parts had been added. Then 250 parts of toluene were added and the mixture heated gently under reflux with progressively increasing temperature, in an apparatus in which the reflux condenser was connected to a trap in which the condensed toluenewater azeotrope collected. The water was separated and removed periodically from the trap and the toluene was returned to the reaction mixture. After no further substantial quantity of water collected in the trap, the toluene was removed from the reaction mass by vacuum distillation.

The product was a heavy oil which solidified on cooling toa hard, brown, glassy and brittle substance having a low softening point (60 C. or higher).

Methods of compounding this product with copolymers of butadiene and styrene (see Composition 1 hereinafter) and butadiene and acrylonitrile (see Composition 2 hereinafter) are are not to be described hereinafter and the efiects produced in such copolymers are tabulated in Table 1.

Example 2.Pentaerythritol diabietate buty ral A mixture of 900 parts of resinous pentaerythritol diabietate and parts of butyraldehyde was heated to G. Then 1.5 parts of oxalic acid were added and the mixture was heated at approximately 100 C. for two hours. Most of the water formed in the reaction was removed during this period. To the reactionmass were then added 100 parts of toluene and the mixture was heated under gentle reflux in an apparatus similar to that described in Example 1, in such manner that the water which distilled over as an azeotrope with toluene was separated from the toluene and periodically removed. After about five hours of heating, during which time the temperature rose from 100 to 150 C., the toluene was removed together with the remaining water.

The resulting product was substantially identical with that formed in Example 1.,

Example 3.-Pentaerythrltol diabietate benzal Pentaerythritol diabietate benzal, the benzal of the partial abietic acid ester of pentaerythritol, was prepared by reacting pentaerythritol with sufficient wood rosin to esterify' approximately one-half of the hydroxyl groups of the pentaerythritol by abietic acid. The mixture of rosin and pentaerythritol was heated slowly to 280 C. in 3 hours. An atmosphere of carbon dioxide gas was maintained over the batch to prevent the formation of oxidation products that darken the color.

The resulting diabietate of pentaerythritol was then reacted with sufiicient benzaldehyde to acetalize the remaining hydroxyl groups of the pentaerythritol by heating the mixture together with a small proportion of hydrochloric acidunder gentle reflux for 1 hour. A small amount of toluene was added prior to heating the reaction mixture in order to suppress foaming. The unreacted benzaldehyde, water and toluene were then distilled from the batch by heating at 200 C. for 30 minutes.

. The product was a hard, brown-colored, homogeneous friable solid that retained a slight odor of benzaldehyde. The yield as 88% of the theoretical.

The eiiects produced byusing this product in the compounding of a synthetic rubber consisting of a butadiene-styrene copolymer (Composition 3) are tabulated in Table 2 hereinafter.

Example 4.--Glycerol abietcte butyral Four equivalents (124 grams) of glycerol were heated with 2 equivalents (690 grams) of wood resin at 250 C. for 2 hours in a fiaskequipped with a mechanical stirrer, thermometer and a steam-jacketed condenser. The mixture was thereafter cooled to C., a water-jacketed condenser substituted for the steam-jacketed condenser, and 3 equivalents (108 grams) of butyra1 dehyde were added together with a small proportion (25 grams) of concentrated hydrochloric acid. The mixture was heated under gentle reflux for Zhours, during which time the temperature of the batch increased from 03 to 96 C. The Water of reaction, .unreacted butyraldehyde and unreacted glycerol were then removed by vacuum distillation at a pressure of 5 mm., during which the temperature rose to C.

The product was a dark brown-colored viscous 7 liquid that retained a slight odor of butyraldehyde.

The efiects produced by incoporating this product in a butadiene-styrene copolymer (Composition 4) are tabulated in Table 2 hereinafter.

Comparison Example 1.D2'ethglene glycol dzabietate butyral The diabietate of diethylene glycol was prepared by heating together at 220 C. for 3 hours a mixture consistin of 318 grams of diethylene glycol and 1035 grams of wood rosin, color N (acid value=162 The diabietate of diethylene glycol was then heated under reflux for 4 hours with a stoichiometric excess of butyraldehyde in the presence of 20 grams of concentrated hydrochloric acid. The unrecated butyralclehyde and water of reaction were then distilled off at a pressure of 5 to mm.

The product was a viscous brown-colored liquid having a slight odor of butyraldehyde.

Results obtained on compounding this product with a butadiene-styrene copolymer (Comparison composition 1) are tabulated hereinafter in Table 2.

Example 5.HaZf-abietates of mixed formals and butymls of pentaerythritol andpolypentaerythritols In this example is used a mixture of partial formals of pentaerythritol and polypentaerythritols that was obtained as a byproduct in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst, which was recovered in accordance with the process described in the application for patent Ser. No. 484,242, filed April 23, 1943, by Karl A. Fisher and Harry Burrell, and which is therein referred to as B-liquor.

To 495parts by weight of the above mixture of formals was added 2000 parts of wood rosin, grade N, which is suflicient to esterify approximately oneehalf of the hydroxyl equivalent of the mixture, and the mixture was heated for 3 hours at 280 C. The resulting product was then cooled to approximately 100 C. and 240 parts by weight of butyraldehyde and 5 parts by weight of concentrated hydrochloric acid (35% HCl) were added. This mixture was then heated under total reflux for 4 hours. The unreacted butyraldehyde and volatile products were removed by distillation at a pressure of several millimeters.

The product was a light amber-colored solid that was tacky and very cohesive.

Incorporation of the product into butadienestyrene copolymers (Composition 5) and the effects produced therein are tabulated in Table 3 hereinafter.

Example 6.-Quarter-abietates of mixed formals and butymls of pentacrythritcl and pol /pentaerythritols Example 5 was repeated but the proportions of reactants were varied so that only half as much rosin was used for the esterification of the mixture of partial formals of pentaerythritol and polypentaerythritols. The remaining hydroxyl groups were acetalized with butyraldehyde,

The effectiveness of this product as compared with that of Example 5 when used in butadienestyrene copolymers (Composition 6) is shown in Table 3 hereinafter.

Example 7.TalZ-oil esters of mixed formals and butyrals of pentaerythritol and polypentaerythritols A mixture of partial formals of pentaerythritol and polypentaerythritols such as was used in Example 5 was esterified with clay-treated tall oil (Trostol, a tall oil marketed by Champion Fibre and Paper Co.) that had the following characterlstics:

Acid number 163 Resin acids per cent 45.2 Fatty acids do 47.3 Combining weight 345 Sterols, etc per cent 7.0 Moisture do 0.6 Ash do 0.35

One hundred seventy (170) parts by weight of the tall oil were mixed with 748 part by Weight of the mixture of partial formals and heated for 2 hours at 275 C. The product was then reacted with butyraldehyde in excess and recovered'as in Example 5.

The product consisted of a dark brown-colored viscous liquid.

The efiects produced on incorporating the product into a butadiene-styrene copolymer (Composition 7) are tabulated in Table 3.

In general, pentaerythritol diabietate butyral and related compounds, to which the present specification is directed, are hard, brittle resinous solids which are generally brown in color, have low melting points or ranges, and low acid numbers (approximately 10 or less). They are soluble in various solvents, such as acetone, xylene, benzene and toluene, and are compatible with linseed oil, petroleum oils, natural and synthetic rubbers and with natural and synthetic resins. They are also compatible with rosin and waxes and may be used as ingredients in the production of sealing wax and similar compositions.

When added to synthetic rubber compositions comprising such materials as butadiene-acrylonitrile and butadiene-styrene copolymers in amounts up to approximately 2 to 3% by weight of the copolymer, pentaerythritol diabietate butyral and related compounds greatly improve the milling characteristics. In amounts up to approximately 40% by weight of the copolymer, the uncured synthetic rubber compositions possess considerable tack and show long fingers but the cured rubber will not be sticky and will retain good nerve. With greater amounts, in excess of approximately 40% by weight of the copolymer, pronounced tack, softening and plasticizing are produced and this tack is retained to a considerable extent after curin or vulcanization. These effects are produced without other significant changes in the properties of the rubber compositions, but the curing time of the composition is generally retarded slightly.

In using pentaerythritol diabietate butyral and the related taokifying compounds of the present invention in the production of synthetic rubber compositions, conventional compounding procedures may be adopted. Except for providing for slightly increased curing periods, no substantial changes in compounding or curing procedures are required. Generally it is desirable to incorporate the tackifying compound directly with the copolymer on the rubber mill by breaking down the copolymer at a suitable temperature, for example, 38 C. F.). and adding the tackifying com pound thereto. The additional compounding ingredients may subsequently be incorporated or blended therein. The temperature at which the milling is most advantageously conducted will be dependent upon the amount of tackifying compound that is added. In some cases it may be necessary to cool or chill the rolls below normal operating temperature because of the softness of the composition.

Preferred methods of compounding the tackifying compounds of the invention and typical synthetic rubber compositions containing such cured at a temperature of 30091. for periods of 15, 30 and 60 minutes, respectively, and the physical properties of the products were determined. In both cases the tackifier was very readily incorporated, the uncured composition had excel lent tack, and the vulcanized product was free from tack.

Identical compositions prepared by the incorporation of dibutyl phthalate instead of the pentaerythritol diabietate butyral were also tested for comparison.

The results are as follows:

TABLEI Modulus, pounds per Ultimate 5% square inch, at per- Tensile 2%; 3 2; Product Cure cent Elongation Strength, E1 eter at 2,223? tion, Hard- 300 F. 300% 500% 700% inch percent ness Butadiene-Styrene 1s 1, sec 870 as Rubber-Pentaerythtitol 30 1, 570 780 65 Diabietate Butyrel 60 l, 640 690 60 (Composition 1.) Butadiene-Acrylonitrile- 2, 205 v 860 65 Rubber-,PentaerytbritoL 2, 700 750 70 Diabietate Butyral 60 3, 140 670 70 (Composition 2.) Butadiene-Styrene. 825 480 50 Rubber-DibutyL l, 030 460 '55 Phthalate 1,145 I 440 55 Butadrene-Acrylonitrlle- 770 -940 45 Rubber-Dibutyl 1,150 990' 60 Phthalate 1, 725 920 55 compounds are illustrated in the examples which cgmpmifion u follow A butadiene-styrene copolymer (GR-S) com- Go mpositioqz 1 One hundred (100) parts by weight of a butadiene-styrene copolymer (GR-S) rubber were rolled on a rubber mill at a temperature of 38 C. (100 F.). While being thus subjected to "break down, 25 parts by weight of the pentaerythritol diabietate butyral tackifying compound prepared as described in Example 1 were added in small proportions during the milling. The composition milled easily and became tacky during the mixing. After the tackifying compound had been thoroughly distributed and incorporated, a mixture of 50 parts by weight of channel black and 5 parts by weight of zinc oxide, 1.25 parts by weight of sulfur powder (flowers of sulfur) and 1.25 parts by weight of a commercial accelerator (Altax) were added during continued milling. The composition was thenremoved from the rolls and was subjected to vulcanization tests.

- The product is sticky and tacky during milling but is free from tack after vulcanization. Physical characteristics of vulcanized products prepared from this composition are tabulated in Table 1 hereinafter.

Composition 2 The foregoing example was repeated but, instead of using a butadiene-styrene copolymer, the composition was prepared from a butadieneacrylonitrile copolymer (GRA) sold under the trade-name Hycar OBI-15. The tackifier was readily incorporated in this manner and the product before curing had excellent tack but was free from tack after vulcanization.

Physical characteristics 01 the vulcanized products prepared from this composition are tabulated in Table 1 hereinafter.

Curing tests of Compositions 1 and 2 Portions of the synthetic rubber compositions prepared in Compositions l and 2 above were position was prepared from the following:

sition 3 except that th glycerol. abietate butyral of Example 4 was used instead of pentaeryithritol diabietate benzal. v p f Physical characteristics. of vulcanized products prepared from this composition arejtabulated in l able 2 hereinafter. v Comparison composition '1 A composition was prepared exactly as Composition 3 except that the diethylene glycol diabietate butyral of Comparison Example 1' was substituted for pentaerythritol fdiab'ietate benzal, weight for weight. l Physical properties of cured products prepared from this composition are tabulated in Tablez hereinafter.

Curing tests of Compositions 3 and 4 and Comparison composition 1 The results ofcuring tests .ofthe three foregoing compositions, which were conducted inthe same manner as the curing, tests of Compositions 1 and 2, are tabulated in Table 2. Y For comparison, the results obtained in such tests with Composition 1 are included. Itis tobe noted, however,

11 that Composition 1 was prepared with a smaller proportion of sulfur and accelerator.

.tyrals of pentaetrythritol and polypentaerythritols whose preparation is described in Example 7 TABLE 2 Modulus, pounds per Mm Ultimate Ulti- Shore utes gggg g g ghg per Tensile mate Durom Product Compounded with GR-S Cure Strength, Elongaeter pounds per tion, per- Hord- 300 F. 300% 500% 700% sq. inch cent ness Pentaerythritol.---.. t 15 335 1, 330 870 55 Diebietate But 30 490 1, 570 780 55 (Composition 1 60 680 l, 640 690 60 Pentaerythritol 15 500 1, 875 800 55 Diabietate BenzaL- 30 l 760 1, 785 600 60 (Composition 3) 60 760 l, 770 590 60 Glycerol Abietatm- 15 545 l, 780 770 55 Butyral 30 800 l, 600 530 60 (Composition '4) 60 510 l, 810 775 50 Diethylene Glycol- 1 5 800 1, 530 500 55 Diabietate Butyrel 30 706 1, 530 495 55 (Comparison Composition 1) 60 745 1, 430 500 55 In all cases, except that of Comparison composition 1, whichis that prepared from a butadienewere substituted, weight for weight, for the tackifying ingredient used in Composition 3 and in otherrespects the composition was prepared as described in Example 3.

Curing tests of Compositions 5, 6 and 7 The results of curing tests of the three toregoing compositions, which were conducted in the same manner as the curing tests of Compositions 1 and 2, are tabulated in Table 3. For comparison, the results obtained in suchtests with Composition 1 are included.

TABLE 3 Modulus, pounds per Ultimate g a square inch, at per- Tensile Egg 32; Product Compounded with GRS Cure cent Elongaeter at pmm tion Hard- F per r I t ess 300% 500% 100% inch De Pentaerythritol 15 l, 330 870 65 Diabietate Butyral... 30 l, 570 780 55 (Composition 1) 60 l, 640 590 60 Hali-Abietates L- l -2, 600 910 65 B-Liquor Butyrai 3D 2, 530 750 70 (Composition 5) (l0 2, 730 560 70 Quarter-Abietates of. l, 600 620 60 B'Liquor Butyrals l, 380 550 60 (Composition 6) 60 1, 680 550 60 Tall-Oil Esters 0f 15 945 630 B-Liquor" Butyral 30 l, 190 490 (Composition 7) 590 840 45 position 1, no tackmess-or only slight taclciness remained in the respective products after curing at 300 F. for the specified intervals.

From the above results it will be noted also that the curingtime is slightlyaccelerated in the case of Composition 3 (that made with the benzal of pentaerythritol diabietate) and that'curing of the others, except Comparison composition '1, was slightly retarded by the presence of the tackifying ingredient inthe compositions.

Composition 5 "A composition w'as prepared exactly as Compositlon 3 except that the halt-abletates of mixed formals andbutyrals of pentaerythritol and poly- The quarter-abietates or mixed formals and butyrals of pentaerythritol and polypentaerythritols '0'! Example 6 were substituted, weight for weight,

for the tacki'fying ingredient used in Composition 3' a'nd'in other respects "the composition was prepared-as describedin Example 3.

-"Composition 7 7 The tall-oil esters of mixed towels and bu- Inall the above compositions (1, 5, 6 and 7) the 'tackifying ingredient was incorporated very readily by the :procedure described and all the compositions possessed excellent tack during milling. No tackiness or only slight tackiness remained in the respective products after curing at 300 F. for the specified intervals, although the sample of Composition 7 that was cured for 60 minues was slightly but definitely tacky. Increasing the time of curing appears to favor development of after-curing tackiness in synthetic rubber composition comprising the tackifiers of the invention.

-In all the above compositions (l, 5, 6 and 7) the curing time was slightly retarded by the addition of the tackifiers, being least retarded by the tall-oil esters of mixed formals and butyrals of pentaerythritol and polypentaerythritols (Composition 7-).

Although the foregoing description comprises preferred embodiments of the invention, it is to be understood that the invention is not limited thereto and that modifications and variations may be made therein without departing substantially from the principles or scope of the invention.

I claim:

1. A tall-oil ester obtained by reacting tall-oil with a mixture of partial formals of pentaerytham -m 13 ritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reactin the product thus obtained with butyraldehyde.

2. A tall-oil ester obtained; by reacting talloil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde in the presence of an acid catalyst.

' 3. A tall-oil ester, substantially free from unreacted butyaldehyde andvolatile products, obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde.

4. A tall-oil ester, substantially free from unreacted butyraldehyde and volatile products, obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde in the presence of an acid catalyst.

5. A dark brown viscous liquid tall-oil ester obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde.

6. A dark brown viscous liquid tall-oil ester obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde in the presence of an acid catalyst.

7. A rubber-like composition containing a butadiene copolymer artificial rubber and a talloil ester obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde.

8. A rubber-like composition containing a butadiene copolymer artificial rubber and a talloil ester obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde in the presence of an acid catalyst.

9. A rubber-like composition containing a butadiene copolymer artificial rubber and a talloil ester, substantially free from unreacted butyraldehyde and volatile products, obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by '11. A" rubber-like composition containing a butadiene copolymer artificial rubber and a dark brown viscous liquid tall-oil ester obtained by reacting a tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde.

12. A rubber-like composition containing a butadiene copolymer artificial rubber and a dark brown viscous liquid tall-oil ester obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde in the presence of an acid catalyst.

13. A rubber-like composition containing a butadiene styrene copolymer artificial rubber and a tall-oil ester obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde.

14. A rubber-like composition containing a butadiene styrene copolymer artificial rubber and a tall-oil ester obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde in the presence of an acid catalyst.

15. A rubber-like composition containing a butadiene styrene copolymer artificial rubber and a tall-oil ester, substantially free from unreacted butyraldehyde and volatile products, obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaterythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde.

16. A rubber-like composition containing a butadiene styrene copolymer artificial rubber and :a tall-oil ester, substantially free from unreacted butyraldehyde and volatile products, obtained by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the presence of an alkaline catalyst and by rea dark brown viscous liquid tall-oil ester obtained 5 by reacting tall-oil with a mixture of partial formals of pentaerythritol and polypentaerythritols produced in the manufacture of pentaerythritol by the condensation of formaldehyde and acetaldehyde in the presence of an alkaline 10 catalyst and by reacting the product thus obtained with butyraldehyde. v

18. A rubber-like composition containing a butadiene styrene copolymer artificial rubber and a dark brown viscous liquid tall-oil ester 013- 15 tained by reacting tall-oil with a mixture of -16 partial formals of pentaerythritol and poly pentaerythritols produced in the manufacture of pentaerythritol by thecondens'ation of formaldehyde and acetaldehyde in the presence of an alkaline catalyst and by reacting the product thus obtained with butyraldehyde in the presence of an acid catalyst. I

' f ROBERT H. EARTH.

REFERENCES CITED The following references are of record in the file 03f thispatent: 

1. A TALL-OIL ESTER OBTAINED BY REACTING TALL-OIL WITH A MIXTURE OF PARTIAL FORMALS OF PENTAERYTHRITOL AND POLYENTAERYTHRITOLS PRODUCED IN THE MANUFACTURE OF PENTAERYTHRITOL BY THE CONDENSALTION OF FORMALDEHYDE AND ACETALDEHYDE IN THE PRESENCE OF AN ALKALINE CATALYST AND BY REACTING THE PRODUCT THUS OBTAINED WITH BUTYRALDEHYDE. 